Most anatomists, biomechanists and good musculoskeletal therapists agree that correct sitting posture (to ensure a happy, healthy spine) should maintain the normal spinal curves – particularly the small curve in the lower back. Unfortunately most occupational health and safety recommendations dictate that the thighs should be parallel to the floor. This position actually results in a flattening of the lumbar curve and since loss of the normal lumbar curve is the primary cause of lower back dysfunction and pain, any position which encourages a flattening of the lumbar curve should be avoided.
Try this: Raise your chair as high as possible, preferably sitting on the front edge allowing your pelvis to roll forwards and creating a nice curve in the lower back. Now either slowly lower the chair via the hydraulic lift or ‘raise the floor’ with a phone book or stool (ideally get someone else to put it in position for you) until your thighs are parallel to the floor. Feel what happens to your lower back. You should notice that the curve is “pulled” out and your back has become somewhat flatter.
Recent research has shown that there is a high correlation between weakness of the deep abdominal muscles and the incidence of lower back pain. If you lean backwards on a stool it is your abdominal muscles which prevent you from falling backwards. By leaning against the back rest on a chair you no longer require your abdominal muscles to work hence, over time, they become weak. Remembering that you have probably been in the habit of using the back rest since you went to school at the age of 5, your deep abdominal muscles have not been used for quite some time!
Tips for correct sitting:
- Raise your chair as high as possible
- Tilt the front edge of your chair down …..this will assist your pelvis to roll forward to maintain a good lumbar curve.
- Use a “Move’n Sit” wedge to increase forward pelvic tilt (see your physio for more information)
- Try to sit on the front edge of your seat…this will assist with weight bearing through the legs improve your abdominal muscle strength
Not only this, but the much reported “Economy Class Syndrome”(E.C.S) of DVT’s after aeroplane flights occur partly as a result of the knees being bent to 90 degrees for a prolonged period. Any liquid traveling in a pipe which bends to 90 degrees will be subject to turbulent flow at the bend…..this type of flow in the blood vessels is a known cause of the thrombosis development. Whilst altitude has a significant role to play in E.C.S, it still makes sense that sitting at sea level with bent knees for a prolonged period is probably not a great idea. Thus raising your chair so that some weight is traveling through the legs and the knee angle is straighter may be life saving as well as back saving.